表語從句講解
表語從句（Predicative Clause）就是用一個句子作爲表語。說明主語是什麼或者怎麼樣，由名詞、形容詞或相當於名詞或形容詞的詞或短語充當表語。
表語從句的定義：
表語從句放在連繫動詞之後，充當複合句中的表語。
表語從句的構成：
關聯詞+簡單句
引導表語從句的關聯詞的種類：
可接表語從句的連繫動詞有be，look，seem，sound，appear等。
China is no longer what she used to be.
今日的中國不再是過去的中國了。
The question remains whether they will be able to help us.
問題還是他們能否幫我們。
At that time，it seemed as if I couldn't think of the right word.
當時，我似乎怎麼也想不出一個恰當的字眼來。
從屬連詞whether，as，as if / though引導的表語從句。
He looked just as he had looked ten years before.
他看起來還與十年前一樣。
It sounds as if someone is knocking at the door.
聽起來好像有人在敲門。
because，why引導的表語從句。
That's because he didn't understand me.
那是因爲他沒有理解我。（That's because…強調原因）
That's why he got angry with me.
那正是他對我生氣的原因。（That's why…強調結果）
what引導的主語從句表示結果或名詞reason作主語時，後面的表語從句表示原因時要用that引導，不宜用because.
The reason why I was sad was that he didn't understand me.
我難過的原因是他沒有理解我。
連接代詞who，whom，whose，what，which，whoever，whatever，whichever
連接副詞 where，when，how，why
The problem is who we can get to replace her.
問題是我們能找到誰去替換她呢。
The question is how he did it.
問題是他是如何做此事的。
That was what she did this morning on reaching the attic.
那就是她今晨上了閣樓乾的。
從屬連詞that
The trouble is that I have lost his address.
麻煩是我把他的地址丟了。
使用虛擬語氣的表語從句
在表示建議、勸告、命令含義的名詞後的表語從句，謂語動詞需用“should+動詞原形”
表示，should可省略。常見的詞有：advice，suggestion，order，proposal，plan，idea等。
My suggestion is that we （should） start early tomorrow.
我的建議是我們明天一早就出發。
應注意的問題：
連繫動詞be，appear，seem，look等之後可以跟表語從句。
It was because he didn't pass the exam.
那是因爲他沒有通過考試。
It seems（that）he was late for the train.
看來他沒搭上火車。
It appears that she was wrong.
看來她錯了。
It seems to me that we should answer for this.
在我看來，我們似乎應該對此事負責。
It appears to her that he wants to teach us all he has.
在她看來，他似乎要把他所會的都教給我們。
引導表語從句的引導詞有以下幾類。
wh-疑問詞
My question is who left.
我想問的是誰離開了。
What I wonder is when he left.
我想知道他是何時離開的。
That's what he wants.
那是他想要的。
This is where they once lived.
這就是他們曾經住過的地方。
That is why he didn't come here.
這就是他爲何沒到這兒來的原因。
whether
My question is whether he left（or not）.
我的問題是他是否離開了。
注：if不能引導表語從句。
that
The fact is that he left.
事實是他離開了。
注：引導表語從句的連詞that間或可以省略。
The truth is（that）I didn't go there.
事實是我沒去那兒。
because，as，as if，as though
It's just because he doesn't know her.
這是僅僅因爲他不認識她。
Things are not always as they seem to be.
事物並不總是如其表象。
He looks as if he's tired.
他好像累了。
